Gas turbines, especially of the stationary or industrial type, usually have an outer housing, which coaxially extends along a machine axis and surrounds a concentric inner carrier, which carries the vanes of the turbine. The outer housing and the inner carrier are separate units, each comprising an upper part and a lower part, both having the form of a half cylinder, which are connected by means of a flanged connection at a common parting plane.
For positioning the inner carrier relative to the outer housing a mechanical connection is established between both parts by means of a plurality of drawers, which extend at certain places through the outer housing to make mechanical contact with the inner carrier.
Document U.S. Pat. No. 3,628,884 A discloses a rotary machine, such as a turbine. The machine comprises a tubular outer casing and a tubular inner casing disposed within the outer casing. The inner casing encompasses a rotating rotor structure.
Hot motive gases, derived from fuel combustion, are expanded as they flow through the machine to drive the rotor structure, as well known in the art.
A plurality of apertures is radially disposed in the outer casing and a plurality of corresponding key slots is disposed on the periphery of the inner casing. After the outer and inner casings are aligned concentrically relative to the axis of rotation of the rotor, a plurality of eccentric bushing structures are radially disposed in the apertures and adjusted to fit the slots to support the inner casing concentrically relative to the axis of rotation of the rotor.
Document U.S. Pat. No. 6,224,332 B1 discloses a turbine having an outer structural shell and an inner shell supported by the outer shell. The inner shell carries an array of nozzles and forming parts of first and second stages, respectively, of the turbine.
To connect the inner and outer shells to one another, each of the forward and aft portions of the inner shell are provided with circumferentially spaced recesses. Support pins pass through access openings through the outer shell for connection with the forward portion of the inner shell. Similar pins interconnect the outer shell with the all portion of the inner shell. Preferably, the pins lie at eight pin locations in each radial plane and are spaced approximately 45° one from the other about the rotor axis. The support pins are also spaced from the horizontal split line of the inner shell. The support pins include an enlarged head having a bolt circle with a plurality of bolt openings, a cylindrical shank and end projections. The support pins support the inner shell from the outer shell for radial and axial expansion and contraction, with the pins carrying only circumferential loadings.
Document US 2009/0226313 A1 discloses a turbine casing structure having an outer casing, and an inner casing disposed in the outer casing, comprising a bush disposed in a concave portion formed in the inner casing; an eccentric shaft inserted into a communication hole formed in the outer casing, and having a front end disposed in contact with the bush; and a fixing member disposed in engagement with the eccentric shaft, and fixed to the outer casing.
Document US 2013/0017082 A1 describes an alignment assembly for mounting and aligning an inner shell within an outer shell. The alignment assembly generally includes a first bushing and a second bushing configured to be received within at least one of an arm extending radially between the inner and outer shells and a boss of the outer shell. The first bushing may generally have an eccentric configuration and the second bushing may include an eccentric portion extending within the first bushing. Additionally, the alignment assembly may include a connection member extending within at least one of said first bushing and said second bushing.
Other assemblies of inner vane carriers and outer housings or casings of turbine are known from documents DE 25 32 537 A1 and DE 42 30 235 A1.
The known solutions have some severe disadvantages:                Due to a lack of mechanical decoupling, requirements on machining precision are very high in order to avoid an unwanted force impact on sensitive portions of the pullable drawers;        Although designs of pullable drawers accessible from outside do exist, these existing designs show often problems due to unwanted force impact on sensitive portions of the drawer.        